In recent years, mobile broadcast and multicast solutions have been standardized by different organizations, such as the 3rd Generation Partnership Project (3GPP) MBMS service. In one aspect, MBMS is a broadcasting multicasting service that may be offered via existing Global Universal Mobile Telecommunication System (UMTS) and/or possibly System for Mobile Communications (GSM) cellular networks. 3GPP MBMS provides the ability to multicast or broadcast data to 3GPP terminals in a cost efficient manner.
3GPP has defined MBMS for the simultaneous delivery of multimedia content to a large set of receivers or user equipments (UEs). A set of MBMS specifications have been published by 3GPP, covering different aspects of the service from the radio access to the content delivery applications and protocols. As part of 3GPP long term evolution (LTE), MBMS is being standardized for the purpose of supporting efficient broadcast services such as, for example, mobile TV services.
LTE MBMS supports an MBMS over a single frequency network (MBSFN) transmission mode. In MBSFN, each base station transmits the same content in a synchronized manner. Operating in this manner, MBSFN enables a highly efficient method of broadcasting, as the transmissions from different base stations reinforce each other instead of causing interference with each other.
In MBSFN, the coverage of data transmission is not limited by cell edge areas, as MBSFN provides a sufficient signal to interference-plus-noise ratio (SINR) gain. Therefore, the capacity of a channel, when delivered as MBSFN transmission, may be significantly larger than when using single-cell transmission.
MBSFN transmission takes place on dedicated subframes (e.g., given the one-millisecond time intervals that all LTE transmissions are divided into, a radio frame consists of ten subframes) referred to as MBSFN subframes, which differ from the regular LTE unicast subframes in that MBSFN subframes contain less pre-specified reference symbols that terminals measure to estimate the channel to the cell. Because of this difference, terminals typically avoid measuring a cell in subframes with the smaller density of reference symbols. For this reason, terminals, regardless of whether they intend to receive MBSFN, need to be made aware of which subframes in the cell are the ones with the reduced reference symbols. To this end, the MBSFN subframe allocation is transmitted in the system information of every cell that also transmits such special subframes.